Manufacture of lubricating oils



MANUFACTURE OF LUBRICATING olLs James Van Dyck Fear, Media, Pa., assignor to Sun Oil Company, Philadelphia, Pa.,' a corporation of New Jersey No Drawing. Filed May 17, 1956, Ser. No. 585,392

This invention relates to the manufacture of lubricating oils, and more particularly to: a combination solvent extraction and dewaxing process-in which a lubricating oil of low aromatic contentand correspondingly high viscosity index is produced.

The manufacture of lubricatingoils by solvent extrac tion and dewaxing of residual and distillate petroleum fractions is well known to the art, and many process variations, using various solvents .both for the solvent extraction and dewaxing steps,.have been proposed. Prior art processes include some in which the oil is dewaxed prior to solvent extraction, and also some in which. the oil is solvent extracted prior to dewaxing. Dewaxing prior to solvent extraction is disadvantageous in that the entire body of the oil must be processed in the dewaxing plant, requiring a large capitalinvestment for processing facilities such as chillers and Wax filters. In addition, more dewaxing solvent is required than in the case where the oil is solvent extracted prior to dewaxing, and the refrigeration costs are much higher.

When the oil is solvent extracted, prior to dewaxing, to the depth required to yield a high V.I. oil upon dewaxing, it will be found that the yield of finished oil and wax will be lower than is obtained when extracting following dewaxing. Nevertheless, in commercial practice, the preferred method of operation has been to solvent extract prior to dewaxing, since the savings obtained in the dewaxing step, due to the smaller volumes processed, more than balance the losses involved in the smaller production of lubricating oil and wax.

It is an object of this invention to provide a process for processing hydrocarbon fractions of lubricating viscosity which minimizes wax plant investment and operating costs, and which also produces a high yield of wax and lubrieating oil of high viscosity index, and an extract which is a high quality carbon black oil.

I have found that this object may be attained by first lightly extracting a petroleum fraction of lubricating viscosity to remove a substantial part of the aromatics contained therein together with a minimal quantity of paraffinic or waxy constituents of the oil, and to substantially reduce the quantity of material to be handled in subsequent processing steps. The raffinate from the solvent extraction is then freed of dissolved solvent, is mixed with a suitable dewaxing solvent, is chilled, and is filtered to remove the wax content. A substantially wax-free, low pour point oil is then separated from the filtrate. The oil so recovered will contain sufficient aromatics to lower its viscosity index undesirably. The bulk of the aromatics was removed by the first extraction, however, so that the load on the wax plant is very little greater than if the original oil had been extracted to a depth sufiicient to yield a high viscosity index filtrate.

The filtrate oil is then subjected to a second light extraction to recover as a secondary rafiinate a high V.I. lubricating oil. Since only a small quantity of aromatics need be removed, only a small amount of solvent need be used, and very little parafiinic material will be extracted. The

7 double extraction according to the present invention gives a higher yield of a higher viscosity index lubricating oil than is obtainable by a deep extraction followed by dewaxing, and the total quantity of materialhandled in the extraction plant (oi-1 plus solvent) is much lower, thus lowering plant investment and operating cost for processing a given amount of oil.

As a further feature of my invention, when treating a light lubricating fraction, such as the bottoms from a distillation of catalytically cracked gas oil, a superior .car: bon black oil may be produced as a by-product. The

value of a carbon black .oil is judged'by its Bureauof and A.P.I. equals A.P.l. gravity at60 F. i

Mines Correlation Index,'and the higher the Correlation Index, usually referred to as 01., the higherthe. .price that can be obtained vfor the oil as a charging stoclg to a carbon black process. C1. is defined as follows:

Where F equals 50% boiling point in degrees Fahrenheit,

In order to illustrate the improved results which may be'obtained iby proceeding according to the present inven: tion instead of by the prior. art method of fully extracting prior to dewaxihg, comparative data for the two processes is illustrated in the following table. The charge stock in both instances was a bottoms fraction from a distillation of the cracked products obtained by the catalytic cracking of a gas oil fraction, and had an initial boiling point (Engler) of 500 F., a 50% point of .800 F., and a point of 920 F., and contained 41% aromatics. All quantities given in the table are based on percent of charge. Furfural was used as the solvent in the extraction step, and the dewaxing Was conducted under comparable conditions as to solvent dosage and temperature in each case.

Table I According According to Present to Prior Invention Art 1st Extraction Step (6 stages):

Solvent Dosage, Vol. Percent Charge" 50 150 Rafiinate Yield 64. 5 58. 5 Extract Yield 35. 5 41. 5 Wt. Percent Aromatics:

E ct 92.0 84. O 13.0 10. 5 129 111 45. 0 41. 0 Wt. Percent Aromatics 18. 5 15.0 Wax Yield 19. 5 17. 5 2nd Extraction Step (6 stages):

Solvent Dosage, Vol. Percent Original harge 23 Ratfinate Yield 42. 0 Extract Yield 3. 0

13. 2 Extract 75.0 0.1. Extract 89. 0

As may be observed from the foregoing data, by proceeding in accordance with the present invention, I obtained a higher yield (42.0% vs. 41.0%) of a refined oil of lower aromatic content (13.2% vs. 15%) and a correspondingly higher V.I., and also increased the Wax yield from 17.5% to 19.5% as compared to a procedure in accordance with conventional practice. The combined extracts amounted to 38.5% of a 125 C1. premium carbon black oil, as compared to 41.5% of a low-quality extract having a Cl. of only 111 obtained from the prior art process. In addition, I am able to substantially reduce the size of the solvent extraction facilities needed, since in accordance with the present process, per volumes of charge, but 218 volumes of oil plus solvent need be Patented Sep t. 13, 19 0 processed, as compared to tracting the charge prior to dewaxing.

While furfural has been in 'cated as the preferred solvent for-removingqaromatics, any other solvent known to the-antmay beused in the extraction step, suchflas phenol, 80;, or other solventsand mixtures thereof Well known to the Since these'other solvents are not as selective as iurfural, the primary rafiinate will probably be larger then when furfural is used, and it may be necessary to extract more deeply in the second extraction step to obtain a high V.I..-1ubricating oil. For these reasons, furfural is the preferred solvent. ,No specific conditions havebeen given for the dewaxingstep, since this step is carried out in a conventional manner using conventional deWaxing solvents and temperatures, and dewaxing, as

such, forms no part of the present invention.

I claim? 7 1 1. 'Processrfor the production of lubricating oil, wax and carbon black oil which comprises contacting a hydrocarbon fraction, derived from catalytically'cracking a gas oil mainly in the range of 500-920 F., with a solvent which preferentially dissolves aromatics, the volume of solvent being less than the volume of oil but sufficient V to. extract a 'preponderant proportion of the aromatics from-said fraction, separating solvent from a first raflinatecontaining wax and unextracted aromatics and irorn the extract to yield a carbon black oil having a high Bureau of Mines Correlation Index, dewaxing the first rafiinate in the presence of a dewaxing solvent and recovering a wax fraction, separating the d'ewaxed first rafiinate from the dewaxing solvent, contacting the dewaxed first rafiinate with a solvent which'preferentially dissolves aromatics, and recovering a high viscosity index lubricating oil as a second raflinate.

250 volumes when fully ex- 2. Process according to claim 1 wherein the solvent which preferentially dissolves aromatics is'furfural.

3 Process for the production of lubricating oil, wax and carbon black 'oil which comprises contacting a hydrocarbon fraction, derived from catalytically cracking a gas oil and boiling mainly in the range of 500-920" F.', with furfural in amount such that theihydrocarbon to turfnral volume ratio is about2z1, separating furfural from a first raflinate containing wax and unextracted aromatics and from the extract to yieldfa carbon black on having a high Bureau of Mines Correlation Index, dewaxing the first raffinate in the presence of a dewaxing solvent and recovering a wax fraction,- separating the dewaxed first r-afiinate from the dewaxing solvent, contacting the dewaxed first rafiinate with furfural in amount such that the hydrocarbon to furfural ratio is about 2: 1, and recovering a high viscosity index lubricating oil :as a second raffinate.

References Cited infthe mana ement Great Sept.. 1 ,1941 

1. PROCESS FOR THE PRODUCTION OF LUBRICATING OIL, WAX AND CARBON BLACK OIL WHICH COMPRISES CONTACTING A HYDROCARBON FRACTION, DERIVED FROM CATALYTICALLY CRACKING A GAS OIL AND BOILING MAINLY IN THE RANGE OF 500-920*F., WITH A SOLVENT WHICH PREFERENTIALLY DISSOLVES AROMATICS, THE VOLUME OF SOLVENT BEING LESS THAN THE VOLUME OF OIL BUT SUFFICIENT TO EXTRACT A PREPONDERANT PROPORTION OF THE AROMATICS FROM SAID FRACTION, SEPARATING SOLVENT FROM A FRIST RAFFINATE CONTAINING WAX AND UNEXTRACTED AROMATICS AND FROM THE EXTRACT TO YIELD A CARBON BLACK OIL HAVING A HIGH BUREAU OF MINES CORRELATION INDEX, DEWAXING THE FRIST RAFFINATE IN THE PRESENCE OF A DEWAXING SOLVENT AND RECOVERING A WAX FRACTION, SEPARATING THE DEWAXED FIRST RAFFINATE FROM THE DEWAXING SOLVENT, CONTACTING THE DEWAXED FIRST RAFFINATE WITH A SOLVENT WHICH PREFERENTIALLY DISSOLVES AROMATICS, AND RECOVERING A HIGH VISCOSITY INDEX LUBRICATING OIL AS A SECOND RAFFINATE. 